The present invention is primarily directed to improvements in vehicular traffic recorders and other information recording systems in which counts of data-representing electrical pulses are stored in a removable semiconductor memory pack. During a traffic counting or other information collecting operation the memory pack is plugged into the recording unit to store the sensed data in binary form. Thereafter, the memory pack is removed from the unit for transportation to a suitable data processing or information gathering center where the stored data is read out.
The removable memory pack feature eliminates the need for returning the entire recording unit to the data processing or information gathering center. The recording unit may therefore remain in the field for further use simply by plugging a fresh memory pack into the recorder unit in place of the one that was removed for return to the data processing center for read-out. After reading out the stored data the memory packs are usually cleared and then may be returned to the field for recording additional data.
With the foregoing type of recording system there is a possibility that in exchanging memory packs the operator of the system will mistakenly place in operation a used memory pack which has not been read out and which contains information from a prior traffic counting or other information collection operation. If this happens new traffic data will be written into the memory over the original data when it is plugged into the recording unit, thereby erasing the original data.
The present invention avoids the foregoing problem as will become apparent from the following summary and detailed description.